1. Field of the Invention
The present invention relates to a catalyst warming control apparatus for a hybrid vehicle, and in particular, a technique for cleaning exhaust gas discharged from a hybrid vehicle which has an electric motor and a internal combustion engine (hereinafter referred to simply as an “engine”).
This application is based on Japanese Patent Application Nos. 11-240592 and 2000-193255, the contents of which are incorporated herein by reference.
2. Description of the Related Art
A catalyst for cleaning exhaust gas discharged from an engine, when it is cold, is not sufficiently activated, cannot satisfactorily perform the cleaning function, and there is a problem that the exhaust gas contaminated with pollutants may be discharged to the air.
Conventional techniques detect the temperature of the catalyst, and activate the catalyst by reducing the engine speed and the load on the engine to restrict the discharge of the exhaust gas when the catalyst is not sufficiently activated according to the measured temperature, or by heating the catalyst when its temperature is low (as disclosed in Japanese Unexamined Patent Application, First Publication Hei 7-79503).
Of the above-mentioned conventional techniques, the technique which includes restricting the engine speed and the load on the engine when the catalyst is cold also restricts the warm-up of the catalyst by restricting the load on the engine. On the other hand, in the technique which includes warming the catalyst by the heater, the heater makes the exhaust system complicated and increases the size of the system. Further, because electric power must be supplied to the heater, there is the problem that the electric power consumption of a battery is increased.